The present invention relates to a deodorizing method for destroying compounds which emit an offensive smell and which are contained in a gas or the like (hereinafter referred to as malodorant components), and to deodorizing catalysts for using of this method.
Examples of a conventional method of destroying the malodorant components contained in gas, include (i) an adsorptive deodorizing method using a porous substance such as activated carbon, zeolite or the like, (ii) a wet-treatment deodorizing method using an oxidizing agent or a reducing agent, or (iii) an ozonolysis deodorizing method and the like.
However, any of the conventional deodorizing methods above mentioned (hereinafter referred to as conventional methods) do not fully achieve satisfactory deodorizing.
More specifically, in the adsorptive deodorizing method, the adsorbent needs to be regenerated or the like since its adsorbing ability expires in a limited period of time. This presents the problem that the deodorizing apparatus requires much labor and expense for maintenance.
The wet treatment deodorizing method involves a troublesome treatment of additives such as an oxidizing agent or the like.
Finally, the ozonolysis deodorizing method includes no such problems as above mentioned, but requires decomposition of ozone admixed with the gas submitted to deodorizing. Sometimes there is insufficient removal of the malodorant components by oxidative destruction and therefore there may be insufficient prevention of environmental pollution, which may provoke respiratory disease or the like.
A solid type catalyst which may be wholly shaped of the catalytic active ingredient, e.g. manganese, titanium and clay in the form of a honeycomb, was used as an oxidative destruction catalyst to remove the malodorant components in an ozonolysis deodorizing method. Accordingly with conventional solid catalyst, however, since the saturated absorption of malodorant components in relation to the catalyst is large, when a condition change occurs, such as in a refrigeration or the like, for example, or when the reaction temperature rises, the concentration of malodorant components becomes low, the malodorant components are released from the catalyst to the air, and, as a result, concentration of malodorant components in the air is increased.
When a gas to be deodorized contains fractions of acid substances, such as nitrogen oxides, lower fatty acids and the like, the acid substances may accumulate on or in the catalyst, or may react with the catalytic components thereof so that the catalyst is deteriorated to an extent such that malodorant components are released in the supposedly deodorized gas.